Petrol prices 'unaffected' by threat to oil giants

Australian Competition and Consumer Commission chairman Graeme Samuel has given major oil companies a week to bring retail petrol prices into line with the benchmark Singapore unleaded petrol price, the major price indicator in Australia.

Petrol prices in Melbourne yesterday were about $1.10 a litre before an expected overnight price rise.

RACV spokesman David Cumming said some would believe that Mr Samuel's threat kept the price down, but petrol was sometimes at its cheapest on Wednesdays.

"It's not unusual, particularly for the supermarket chains, to be selling below cost with a discount coupon on that day of the week," he said.

"I have seen nothing untoward in the Melbourne market this year and for most of last year. Prices come down on Sunday and go up on Wednesdays - that's how it works."

Yesterday's cheaper petrol may have been caused by a drop in the wholesale price and the sometimes erratic nature of the pricing cycle.

"The proof will be in whether or not the jump will be the normal 12 cent jump that we have been having of late," Mr Cumming said.